Urea, ammonia, and nitrate (UAN) are gradually replacing anhydrous ammonia as the preferred nitrate fertilizer. As a result, ground water contaminated with UAN is becoming more common. Such contaminated ground water may be found underlying commercial fertilizer dealerships and storage areas and in waters around agricultural areas of the United States, including Iowa, Illinois, Nebraska, Minnesota, Indiana, Texas, and California, as a result of runoff.
Ground water containing UAN can be pumped from the ground and used for crop irrigation, with the UAN serving as a source of fertilizer for the crops. Although irrigation presents a use for UAN contaminated ground water, it does not always present a feasible alternative use. Additionally, runoff or other discharge of the irrigation water to nearby surface waters must be avoided to prevent degradation of the water quality. The presence of nitrogen compounds in surface waters can be detrimental because the nitrogen compounds serve as a nutrient source for undesirable phytoplankton and phytobacteria and can lead to fouling of the water, including eutrophication. For example, ammonia in low concentrations is extremely toxic to fish. Ammonia in ground water can also be nitrified to nitrate and in the nitrate form is toxic to infants. Thus, it may be desired to treat the ground water to reduce the concentrations of nitrogen compounds.
Waste water streams that are discharged from industrial sites such as fertilizer factories, dye factories, livestock feed factories, and electric power plants are known to contain inorganic and organic nitrogen compounds, including ammonia, hydrazine, nitric acid, nitrate, nitrite, and urea. The concentrations of the nitrogen compounds typically can be very high. Because of the high concentrations of nitrogen compounds percolation of theses wastes adversely affects ground water quality. As a result, conventional methods for treating such waste water can be complex and costly.
There remains a need for an efficient, cost-effective method for treating ground water to reduce the concentrations of nitrogen compounds present in the ground water. There also remains a need for treatment processes that avoid the formation of harsh chemicals as byproducts, thereby allowing for the environmentally safe discharge of the ground water.